TEC powering question
 

I'm planning my TEC setup for cooling my CPU and GPU. I've got a 120 watt peltier for my CPU, it's 24V 8.4A. I'm getting all 24V fans for my case and radiator, so I can power them all off a 24V meanwell rated at 10A. The fans aren't pulling much amps ~.06-.05A, so I'm fairly certain I'll only be slightly over the 84% efficiency rating. I'm not worried about that setup.

I'd like to run an 80 watt, 15.2v TEC for the GPU. I don't want to run three PSU's in my case and was wondering what affect it would have, if any, on any other components in my PC, like HDs, CD-Drives and that sort of stuff. I'd like to use Enermax's new EG425P-VE SFMA, which has 2 12v rails. One for the motherboard and the other for drives and that kind of stuff. If I put the TEC on the same rail as the drives, which wouldn't be more than 2 WD HD's pulling little more than 1A, and a CD-R/W pulling 1.5A, would the TEC do anything bad to the drives?

TECs don't induce any interference on a power rail, that I'm aware of. I believe it should be ok.

By the way... if your 120W TEC is rated for max 24 volts, you'll want to run it under that.

I know, but 18V-15V is actually more expensive. I can adjust it to about 10% lower, so ~21.5V. Also, I've never read anything that stated that running a TEC at it's rated voltage would damage it, it just isn't as effecienct as running it at 75%. The jump from 75% to 100% isn't dramatic enough to warrant it. Thanks for the info.

crap
if you really want thah much heat moved you can run flat out
-> better have a good cooling system though

Ben - no data, no comment (I previously posted such in the Flowers thread)

I would recommend something beefier than a 120W TEC for your CPU....

It shouldn't be putting out that much more than a 226W pelt, ~10-15W more. It should give me a good idea of what I'd need to do if I stepped up to a 172+W pelt in the future. My main concern is not the CPU pelt, it's the GPU pelt running off the same rail as harddrives and cd-r/w drives. Most of the pelt systems I've seen have used seperate psu's. Even my oldschool days of cele-300a pelt cooling was always with a seperate psu. I was just wondering if getting a psu with a seperate rail would help me or not. If there's no noticable noice introduced I could possibly save a few bucks on the psu. Anyways, thanks for the reply.

I understand that most pelts used to cool cpu's these days are 172+W, but I've got the 120W and the psu. I might not get stellar temps, but it'd be better than just using straight watercooling, granted that I have adequate cooling for the setup to begin with.

Bit off topic, but I didn't want to start a new thread.

Has anyone used type-88 electrical tape to cover their motherboard around the socket for condensation prevention? I don't want to put anything on my motherboard what would become a pain in the arse, if I needed to clean it all off. I figured I could use electrical tape to cover the actual components and then cover the tape with some 3M Scotchkote Electrical Coating to make it moisture resistant. I was just wondering if any EE's, or electrical tradesmen, out there had used it before and what they thought. I'm going to cover a section of a NIC card to test it out this afternoon, but if anyone has any thoughts before then, I'd love to hear them.

I've heard of people using "Liquid Electrical Tape", which is probably the same thing you're going to use.

Not neccessarily, if your CPU is putting out close to 120W itself then using a 120W TEC is actually worse than no TEC at all. You didn't mention which cpu it is, but most any CPU will be putting out 60W+ at stock, let alone once you start cranking up the clocking.

I'm running a 2.8Ghz/533Mhz Intel P4. Intel's specs state that it puts out 68.4W@1.525V. It'll hit 3.12Ghz@1.525V, but even going up higher shouldn't go much over ~100W. We'll see.

I just wish there was a good way of determining how much wattage a CPU puts out, while it's actually running. Maybe Intel, or a motherboard maker, can come up with some kind of built-in monitoring device that would show you the amperage your CPU was consuming. Oh, well, enough pipe dreams...

Roughly speaking it increases proportional to cpu frequency. So if it's 68.4W at 2.8G, it'll be roughly 68.4*3.12/2.8 = ~76W at 3.12W. Voltage has a much more significant impact on power consumption. It used to be proportional to the square of the voltage, though I'm not sure how accurate that if for more recent cpus. That would mean increasing to 1.6V at 3.12G would give: 76*1.6²/1.525² = ~84W.

Ok. Successfully coated a NIC with that Scotchkote stuff and fired it up without any hitches. I'll use it to coat the area around my socket when I start installing the pelt. I took some pictures, since I have nothing else to do and I like using my Dad's camera.

76W sounds within reason for a 120W pelt. Won't get stellar temps, but we'll see what happens. Thanks for the algorithyms!

I roughed out a calc with a handy peltier calc I have and estimated around 20C for a 76W load on a 120W TEC with 25C ambient, so not bad.

Kryotherm results (75W heatload, Ambient = 25C, Rh = .18. Rc = .1, Rins = 1) for a Drift 1.15 pelt (120W, 24.6V)

@24 volts:
Thot = 73.3
Tcold = 25
Tcpu = 31.8
@21 volts:
Thot = 65.1
Tcold = 23.8
Tcpu = 30.7
@15 volts:
Thot = 51.6
Tcold = 25.3
Tcpu = 32.1

It's worth pointing out that going from 15 to 21 volts has a cost of about 75 additional watts dumped into the loop.

Looks like I have a couple of temps to beat.:) I probably won't have it up and running by this weekend, but I'll throw up some pics of the system, pre, during, and post build for you to google at. I'm aiming for 15C idle...

Low idle temps are easy - the cpu puts out a fraction of it's load power.

Were you estimating full load temps, then? That really doesn't sound that bad then. Only time will tell. It's getting hard to wait till the weekend, but if I start now I won't get any sleep till the weekend, and that's just bad.

You've just got too much blood in your caffeine system.

Yes, those were full load temps. ;)